The present invention relates in general to connectors for connecting the ends of pipes and tubes together, and in particular to a new and useful sleeve connector which includes a socket part for one tube having a conical surface and a locking member having a cylindrical surface for engaging around the end of another pipe, and a toroidal surface for engagement against the conical surface of the socket.
In pressure tubes and fittings including sleeve connections, forces occur which result from the inside pressure and must be taken up at the end points, bends, or branching points either by the surrounding ground or by a proper locking. For transmitting very strong forces such as occurring in large-diameter pipelines or under high operating pressures, sleeve connections are employed which are secured against shift and in which a positive connection transmits the forces. For this purpose, the spigot of one tube to be introduced into the socket of another tube is provided with a retaining collar, mostly in the form of a weld deposit, and the socket end is provided with an annular recess in which a locking part is received.
In a prior art sleeve connection of this kind, (German Pat. No. 22 05 000), the annular recess has on its side close to the socket end a tapering surface and the annular locking part has a cooperating taper. This has the advantage that with any mismatching due to manufacturing tolerances, between the axially exactly aligned socket and spigot ends, the forces will be transmitted uniformly over the entire circumference of the locking part. However, such sleeve connections must also be capable of angling, within limits. That is even if there is a small angle between the tubes to be connected. In such instances, a full contact between the tapering surfaces is no longer ensured. With an angled connection and under strong lengthwise acting forces, high local force and stress peaks occur which may result in a failure of the shift security or even in a deformation of the spigot end.
In other prior art sleeve connections, attempts have been made to avoid such drawbacks by providing spherical surfaces for transmitting the forces, having common centers at locations where, in an angled position, the axes of the two tubes intersect (German Pat. Nos. 18 17 319 and 20 16 440 and German OS No. 21 62 435). A spherical joint thus formed transmits the axial forces uniformly over the entire circumference of the socket, even in an angled connection. However, this is true only for connections having exact nominal dimensions.
In practice, nominal dimensions are found in sockets and spigots to be connected to each other only on extremely rare occasions. Connections must be made for tubes having dimensions which, within permissible tolerances, depart from the nominal values. For example, with a nominal diameter of 400 mm, variations of up to 4 mm may occur. As a result of inaccuracies in dimensions, the centers of the spherical surfaces of the recess and the locking part are displaced relative to each other to an extent interrupting the continuous surface contact therebetween. Locally excessive forces and stresses are produced which are capable of deforming the spigot or shearing off the weld deposit thereon, with the result of a failure of the connection.